720 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS PE PP OPP % oo. Id hd i Figure 6 Permeated quantity of the vapour over an odorous product relative to the original com- position. component from the value for the average total, the lowest being 2.0% for peak 2, the highest being 30.4% for peak !3. The ratio of the permeation through PE hd, determined in the same way, was shown to be 0.8% 1.3% with PP, and 0.9% with OPP. Comparing these values one must consider that the thickness of the plastic films tested were different. It is striking that with OPP, for instance, the relative permeation of component 2 is many times greater than any other of the six components under consideration, while in case of PE ld the same component per- meated far less than any other. The deformation of the composition of vapours over odorous products, by permeation through plastic films, is shown to be rather dependent on the film material. The fraction per component of the total of all six components preceding, and following, permeation through the four plastic films is shown in per- centages in Fig. 7.

CHANGES IN COMPOSITION OF VAPOURS OVER ODOROUS PRODUCTS 721 I I , 1 © © © © © © © © © © © © © © © © © © © © © © © ©